[Python-Dev] Comparing PEP 576 and PEP 580

[Jeroen Demeyer]

On 2018-07-04 03:31, INADA Naoki wrote:
> I think both PEPs are relying on FASTCALL calling convention,
> and can't be accepted until FASTCALL is stable & public.

First of all, the fact that FASTCALL has not been made public should
not prevent from discussing those PEPs and even making a
(provisional?) decision on them. I don't think that the precise
API of FASTCALL really matters that much.

More importantly, I don't think that you can separate making FASTCALL
public from PEP 576/580. As you noted in [1], making FASTCALL public 
means more than just documenting METH_FASTCALL.

In particular, a new API should be added for calling objects using the
FASTCALL convention. Here I mean both an abstract API for arbitrary
callables as well as a specific API for certain classes. Since PEP 580
(and possibly also PEP 576) proposes changes to the implementation of
FASTCALL, it makes sense to design the public API for FASTCALL after
it is clear which of those PEPs (if any) is accepted. If we fix the 
FASTCALL API now, it might not be optimal when either PEP 576 or PEP 580 
is accepted.

Jeroen.


[1] https://mail.python.org/pipermail/python-dev/2018-June/153956.html